Laser Welders for Defect Repair

Jewelry Porosity & Crack Repair

Pits, voids and hairline cracks are the defects that decide whether a piece is saved or sent back to the melt. This page is about reading the defect first, then choosing the machine that can rebuild it — not about sending the work out.

Identify the Defect Repair or Recast?

Rebuilding

Not Just More Power

Local Defects

Not a Substitute for QC

Before Scrap

Recover the Casting
Start Here

What Type of Defect Are You Repairing?

Porosity and cracks are repaired differently, and within each there are kinds that behave differently again. Naming the defect is the first decision, because it changes everything that follows.

Macro of an unpolished cast gold surface showing a cluster of small pits and voids

Porosity: voids left in the metal, opening up as you cut and polish.

Macro of a fine hairline crack running across a polished white gold ring shank

Cracks: a separation that runs, and that will keep running if only filled at the surface.

Porosity
Surface Porosity

Small pits that appear as the skin is cut back. Often shallow, and usually the most straightforward of the group — but only once you have established that it stops where you can see it.

Porosity
Casting Voids

Larger cavities from incomplete fill or shrinkage as the metal solidified. These can run deeper than the opening suggests, which is why depth is checked before any metal is added.

Porosity
Gas Porosity

Fine, often rounded pockets from gas trapped during casting. They tend to be distributed rather than isolated, so opening one frequently reveals more alongside it.

Crack
Hairline Cracks

A thin separation with very little to weld into. The visible line is usually shorter than the actual crack, so the extent is established before it is closed.

Crack
Shank Cracks

Cracks in the band, often from sizing, stress or thin sections. The shank carries load in wear, so a repair that only closes the surface tends not to hold.

Crack
Setting Cracks

Cracks in or beside a setting, where a stone limits how the repair can be approached. Both the defect and the stone have to be assessed before work starts.

The Decision Before the Repair

Repair or Recast?

Not every defect should be welded. Getting this call right early is what keeps a bench from spending an hour on a piece that was always going back to the melt.

Leans toward repair
Local, bounded, reachable

The defect is isolated rather than spread through the section. There is sound metal around it to weld into. Enough wall thickness remains once the defect is cut back. The area can be reached and finished after welding. A single piece, or a small number, where recasting costs more than the repair.

Leans toward recast
Spread through the metal

Porosity appears again each time you cut deeper — a sign it runs through the section rather than sitting in it. Cracks through a load-bearing area of a thin shank. So little wall left after cutting back that the piece would be weak anyway. A defect repeating across a whole batch, which points at the casting process rather than the piece.

The honest limit

Laser welding is for local defects. It does not replace proper casting quality control, and a machine bought to paper over a casting problem will simply be busy forever. Where a defect repeats batch to batch, the fix belongs upstream.

A jewellery piece held under the microscope of a laser welding station
Assessment

What to Check Before Welding

Six readings taken at the loupe, before the first pulse. Each one can change the answer to Repair or Recast.

Depth of the defect

How far it goes, not how big it looks. A pit that keeps opening as you cut back is telling you something the surface was hiding.

Extent across the piece

Isolated or distributed. One void is a repair; a scatter across the whole section is usually a casting question.

Remaining metal thickness

What wall is left once the defect is cut back to sound metal. This is what decides whether the finished piece can carry load in wear.

The alloy

Karat, colour and whether it is a known mix. Unmarked or reclaimed metal behaves unpredictably and is worth testing on an offcut first.

Old solder joints

Earlier repairs sit at a lower melting point than the parent metal and will move before it does. Finding them first is cheaper than finding them during.

Stone positions

Where the stones sit relative to the defect, and what they are. On set pieces this often decides the approach more than the defect does.

Two Different Jobs

Porosity Repair vs. Crack Repair

They are often spoken of together and handled as if they were one job. On the bench they are not.

On the benchPorosity repairCrack repair
What the defect isMissing metal — voids where the casting failed to fill or gas was trapped.Separated metal — a fracture running through material that is otherwise present.
What the repair doesRebuilds volume. Metal is added back layer by layer until the void is filled with sound material.Rejoins the two faces along the length of the crack, then adds metal only where the prepared groove needs it.
PreparationCut the pit back until sound metal is reached on all sides. Welding over an unopened void traps it.Establish where the crack actually ends, then open a groove along it. The visible line is usually shorter than the crack.
Where it goes wrongFilling the mouth while the void continues underneath — it reopens at polish.Closing the visible portion only, leaving the tip to run again under load.
What the machine needsRepeatable low-energy pulses and clean filler feeding, for many small deposits in sequence.Control along a line rather than at a point, with enough penetration to reach the root of the groove.
After weldingCut back and re-inspect. A second pass is normal rather than a sign of failure.Check that the repair reaches the full depth before finishing, not just that the surface looks closed.

The sentence worth remembering

Porosity repair is about controlled metal rebuilding, not simply higher laser power. Turning the energy up fills faster and traps more; it is the wrong lever on this job.

Why It Comes Back

Common Repair Problems & Why They Happen

The failures benches report most, and the cause behind each — including the question of why porosity reappears after it was supposedly repaired.

Reappears
Porosity returns at polishing

The mouth of the void was filled while the cavity continued below it. Polishing cuts back into the trapped space and opens it again. The cure is preparation, not more power.

Reappears
The crack runs again

Only the visible length was closed. A crack tip left unwelded is a stress concentration, and load finds it. Establishing the true extent first is the whole job.

Process
New porosity created by welding

Too much energy, a contaminated surface or gas drawn into the pool can leave voids in the weld itself. Clean preparation and lower, repeated pulses give a sounder deposit.

Material
Old solder moves first

An earlier repair melts below the parent alloy and shifts before the surrounding metal responds, pulling the area out of shape.

Finish
Colour mismatch at the repair

Filler from a different alloy family reads differently once polished. Matching karat and colour to the parent metal avoids a repair that is sound but visible.

Upstream
The same defect across a batch

When every piece from a pour shows it, the problem is the casting, not the piece. Repairing the batch treats the symptom and hides the cause.

Two Ways to Put Heat In

Laser Welding vs. Torch Repair

Both are used for defect work, and many benches use both. The difference is what happens to the metal around the repair.

TorchJewellers torch soldering setup on a workshop bench
LaserGloved hands positioning a ring in the work chamber of a jewelry laser welder
On the benchTorch repairPulsed laser welding
Heat into the pieceThe section is brought up to temperature, so the whole area is affected.Energy is deposited at the aimed spot, with much less carried into the surrounding metal.
FillerSolder, at a lower melting point than the parent metal.Wire of the same alloy family, so the rebuilt area matches what is around it.
Building volumeAwkward for filling voids — solder flows where it is drawn rather than where it is placed.Suited to it: metal is placed pulse by pulse, which is what void filling actually needs.
Set piecesStones commonly removed first, then reset afterwards.Often welded with stones in place, subject to assessment of stone and distance.
Working near old jointsEarlier solder in the area is likely to move.Heat can be kept off an old joint alongside the repair.
Where torch still winsLarge joins, bulk work and pieces with no stones and no nearby joints — quicker to set up and cheaper to run.Slower per repair on large work; the advantage is control, not speed.

This compares methods, not products. Most benches doing mixed work keep a torch as well.

Specification Brief

What to Look for in a Porosity & Crack Repair Laser Welder

Defect repair asks for different things than joining does. Each item below is described by what it changes when you are rebuilding metal rather than closing a seam.

Read the full buying guide
Small controllable spot
Void filling is many small deposits placed precisely, not one large one. A spot you can keep inside the prepared cavity is what stops the repair spreading across sound metal.
Adjustable pulse width
Rebuilding wants a longer, softer pulse than tacking does. Being able to change the shape of the pulse — not only its energy — is what separates a sound deposit from a spattered one.
Fine pulse control
Enough to melt the filler and fuse it to the wall of the cavity, and no more. Excess energy is the most common cause of porosity created during the repair itself.
Stable output at low energy
A void is filled over many pulses. If the tenth differs from the first, the deposit varies through its depth. Repeatability matters more here than a high ceiling.
Microscope clarity
You are working inside a cavity a fraction of a millimetre across and checking whether it has bottomed out. What the optics cannot resolve, the operator cannot judge.
Filler wire control
This is the core of defect work. Feeding matching wire cleanly, pulse after pulse, is what rebuilding means in practice.
Parameter storage
Each alloy and each defect type wants its own settings. Recalling a proven one keeps results consistent between jobs and between operators.
Duty cycle and cooling
Batch recovery work runs long sessions of repeated pulses. Stable cooling is what keeps the hundredth repair the same as the first.
Workshop tray of freshly cast unpolished gold jewellery pieces with sprue stubs still attached
For Production Teams & Casting Rooms

Recover Defective Castings Before You Scrap Them

In a production setting the question is not one ring, it is what share of each pour gets rejected and where that metal and labour goes.

Scrapping costs more than the metal

A rejected casting has already taken wax, investment, a pour and finishing time. Refining recovers the metal; it does not recover any of the rest.

Sort before you decide

Local, bounded defects are candidates for recovery. Pieces where the defect runs through the section are not. Applying the same triage the bench uses — depth, extent, remaining wall — turns a reject bin into two piles.

Consistency is what makes it viable

Batch recovery only works if the hundredth repair matches the first. Stored parameters, stable cooling and repeatable low-energy output are the specifications that decide this, which is why they sit above peak power for production buyers.

It is still not a substitute for QC

Recovery buys back pieces already cast. When the same defect appears pour after pour, the answer is upstream in the casting process — a welder used to hide that will just run continuously.

See the High-Volume tier

Send Us a Defective Piece for a Free Sample Test

Send a piece you would otherwise scrap — a porous casting, a cracked shank — and we will attempt the repair and return it with the parameters we used, so you can judge the result on your own metal rather than on ours.

Arrange a Free Sample Test
Questions Buyers Ask

Frequently Asked Questions

Almost always because the void was closed at the mouth while the cavity carried on underneath. Polishing then cuts back into the trapped space and opens it. The fix is in the preparation — cut back to sound metal on all sides before adding any — rather than in more laser power.

We will not put a figure on that. What determines the answer is how much sound metal remains once the defect is cut back, whether the filler matches the parent alloy, and whether the weld reaches the root rather than just the surface. Where too little wall is left, recasting is the better call — which is what the Repair or Recast section is for.

Using filler from the same alloy family avoids the colour mismatch that solder leaves, but the area still needs the normal cutting back, emery and polishing. How well it blends comes down to the finishing as much as the weld, and a large rebuilt area is harder to lose than a small one.

No — this is the most common misunderstanding on this job. Porosity repair is controlled metal rebuilding. Raising the energy fills faster, spatters more and is itself a cause of fresh porosity in the deposit. Pulse shape, repeatability at low energy and clean filler feeding matter more than the top of the range.

It can recover pieces that have already been cast with local, bounded defects. It is not a substitute for casting quality control. If the same defect appears pour after pour, the cause is upstream, and a welder bought to cover it will simply run continuously without the reject rate changing.

Take the six readings in the assessment section — depth, extent, remaining thickness, alloy, old joints, stone positions — and use the Repair or Recast comparison. If you would rather test it than judge it, send us a piece you were going to scrap and we will attempt it.
Get In Touch

Request a Quote for Your Bench

Tell us the defect work you take on — the alloys, the kinds of porosity or cracking you see, and whether this is bench repair or batch casting recovery — and we will come back with a shortlist of models and a configured quote.

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